The present invention relates generally to a magnetic recording/reproducing apparatus for recording or reproducing information with a magnetic tape being wrapped around a guide drum.
Recently, improvement for current home-use video tape recorders (VTR) is being made for further size-reduction purpose without changing the recording pattern on a magnetic tape. One approach to size-reduction of VTRs is disclosed in U.S. Pat. No. 4,614,985 issued to the same assignee in which a magnetic tape is wrapped around a guide drum ranged about 270-degrees rather than about 180-degrees for the current VTRs and four video heads are provided at an angular distance of 90-degrees each other to reduce the diameter of the guide drum to two-thirds of that of the current VTRs.
For keeping the tape interchangeability with the current VTRs it is required that the standard track patterns of video signals to be recorded on a magnetic tape are kept identical to each other and further the length of magnetic tape in the tape path from the guide drum to the audio/control signal head (A/C head) are coincident with the standard length in terms of agreement of tracking servo control.
An example of tape loading mechanism for a magnetic recording/reproducing apparatus showing the above approach for the improvement is disclosed in U.S. Pat. No. 4,626,938 which is assigned to the assignee of the present application. This is arranged for the travelling of a magnetic tape with a pinch roller coming into pressure contact with a capstan such that a play bar is operated in accordance with rotation of a cam effected by a motor and a pinch roller arm having a pinion is rotated by a predetermined angle in response to the straight movement of a pinch roller bar having a rack coupled through the play bar to a spring so that a pinch roller is brought into resilient pressure contact with the capstan.
In such a pinch roller drive mechanism made up of a number of parts, since the pressing force of the pinch roller to the capstan depends upon a force generated due to extension of the spring, the spring force is directly applied to the cam, play bar and engaged portion, and hence it would be required in design to sufficiently consider the strengths of the gears and so on. Thus, the cam, play bar and gears become greater in weight as enough to maintain the rigidity against the loads applied thereto. Furthermore, if the rigidity of the gears is low, the engaged portions are worn away with the passage of time to cause increase in backlash and hence it is impossible to keep the stable rotation of the pinch roller arm and the required pressing force of the pinch roller.